The Atlantic Elite Range consists of 3 Lever Sashlocks, Euro Sashlocks and 5 Lever Sashlocks British Standard BS3621, all in 2.5? and 3?. A sashlock has a deadbolt within it that locks the door by turning the key. It also has a latch built in so that the door will stay closed in the frame unlocked. A 3 lever lock has 3 levers that move into position when the key is entered and turned in the lock, whereas a 5 lever lock has 5 levers offering extra security. 5 Lever locks are usually fitted on external entrance doors. 3 lever locks are often fitted internally, perhaps between a home and garage. A Euro Deadlock is a deadlock where the locks is operated by the Euro Cylinder with one full turn of the key.